PRO FILTER Premium Air Filters are made of chemical resistant, high quality polyester based foam. Dual-stage design allows for superior filtration by eliminating the passage of fine dirt and dust, while helping to prevent air flow blockage. Special reticulation process offers unsurpassed air flow and filtration. Industrial strength, resin bonded seams increase the integrity of the filters wash after wash. Packaged individually in a re-sealable bag.